Benedict Cumberbatch joined Extinction Rebellion (XR) protesters camped out in London on Wednesday night.
The Doctor Strange actor, who is currently filming the movie Louis Wain in the British capital, was pictured speaking to activists from the group in Trafalgar Square, as they camped out for the third night of a planned two-week protest against government inaction on climate change.
Photographs posted by members of XR on Twitter showed the star, wearing a beige flat cap, smiling and joking with the activists.
According to London's Evening Standard newspaper, Benedict spent a "good couple of hours" at the camp.
XR protests have taken place in cities across the world are calling for urgent action to save the environment.
Other stars who have attended the British protests include the model Daisy Lowe, as well as actors Mark Rylance and Juliet Stevenson.
Members of bands The Wombats, Disclosure, and Mystery Jets are among the acts who have performed impromptu gigs at the London camp this week.
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